The present invention relates to an electromagnetic pickup device for a stringed musical instrument and the like wherein a vibrated string of magnetizable material disturbs the magnetic field of a permanent magnet which induces an electromotive force in a coil for later amplification and acoustic transduction.
In known electromagnetic pickups, such as those disclosed in U.S. Pat. Nos. 2,896,491, 2,909,092, 2,968,204, 2,976,755, 3,236,930, 3,290,424, 3,535,968, 3,588,311, 4,026,178 and 4,133,243, a plurality of coil pole pieces, which are in contact with a permanent magnet, each have an end portion facing one string of a musical instrument. The disadvantages of this type of pickup device is that the magnetically active area for coacting with the strings is very small and the output of the device is extremely sensitive to the position thereof relative to the strings.
In U.S. Pat. Nos. 3,657,461 and 4,050,341, pickup devices are disclosed wherein a simple pole piece is used which is surrounded by a coil and has insulating layers thereover. The disadvantages of these types of devices is that although they are less position sensitive, the magnetically active area is still small, resulting in weak signals for amplification. Such devices of the past have also been complex to construct and require the labor and material necessary to provide the individual pole pieces. Where longitudinal bars have been provided, they have been limited to sizes to fit internal of the windings of the coils of the pick up.